The present disclosure relates generally to heating, ventilating, and air conditioning (HVAC) systems that use HVAC devices to serve thermal energy loads (e.g., heating loads, cooling loads, refrigeration loads, etc.). The present disclosure relates more particularly to capacity limits for HVAC devices.
Capacity limits for HVAC devices define a maximum output that be provided by the devices. For example, the capacity limit of a chiller may define the maximum cooling load that the chiller can provide. Capacity limits are typically used in a HVAC system to determine how many devices are needed to satisfy a given thermal energy load. For example, if a chiller has a capacity limit of 3000 tons, a controller for the HVAC system may determine that multiple chillers are required to satisfy a cooling load in excess of 3000 tons. If only one chiller is currently active, the controller may activate an additional chiller to help satisfy the cooling load.
Capacity limits are typically determined by device manufacturers based on manufacturer testing of the devices under design conditions. Capacity limits based on design conditions are referred to herein as design capacity limits. The design capacity limit for a HVAC device may be inaccurate when the device is operated under conditions that differ from the design conditions. The actual capacity limit for a HVAC device may depend on the actual conditions at which the device is operated (i.e., actual operating conditions) and may be unknown in many implementations. Differences between design capacity limits and actual capacity limits for a set of HVAC devices may result in a suboptimal utilization of the HVAC devices to serve a thermal energy load. It is difficult and challenging to identify and effectively use the actual capacity limits for HVAC devices under many operating conditions.